OD&D or B/X for dungeon-crawling, Barbarians of Lemuria/Everywhen for just about everything else.

Quote from: Omega;1113094BX D&D)

When I introduce my nephew to RPGs, I plan to use the B/X rules.

Some days I'd say OD&D, via White Box - Fantastic Medieval Adventure Game.

Other days, I might say Dungeon World.

Truth is; the game is more in my head, than in the book.

Toon and low-level BECMI/RC D&D.

I'd be tempted to run space opera using a hacked Toon rule set--if I were inclined to run space opera.  It would "work", too, though that's because I'm incapable of taking space opera even remotely seriously.

D6/Mini Six followed by Advanced Fighting Fantasy.

I like FUDGE using only D&D stats and Betrayal dice. TWERPS for one-shots or just messing around (it's surprisingly robust and combat has actual grid-based tactics.)

The best overall system is probably something similar to Arneson's Blackmoor, whereby you roll 2d6 stats (you make up the stats as they come into play) and weapon skills. Roll equal or under for success. HD represents both hit points and damage rolls. AC is a saving throw. All magic is alchemical (collecting super berries, lol) and is available to everyone with training. No classes*. XP is equal to monster's HP. Ex., you kill an orc with 4 hits points, congrats, you get 4 XP. 1000 XP per level to advance. Perfection.

*In a modern sense, every PC was a dual-class Warrior/Wizard with levels in each, if desired.

Chivalry and Sorcery of course!

Real answer, probably Toon. Rules can be learned in about two seconds, always fun as hell to play.

Quote from: Steven Mitchell;1113138Toon and low-level BECMI/RC D&D.

I'd be tempted to run space opera using a hacked Toon rule set--if I were inclined to run space opera.  It would "work", too, though that's because I'm incapable of taking space opera even remotely seriously.

Didn't even see this...Toon is ridiculously robust.

Tiny D6 is very rules light and was an absolute delight to play (played a half dozen sessions of Tiny Wastelands). I have not had a chance to run with the system yet, but the simplicity really appealed to me.

Quote from: Nihilistic Mind;1113160Tiny D6 is very rules light and was an absolute delight to play (played a half dozen sessions of Tiny Wastelands). I have not had a chance to run with the system yet, but the simplicity really appealed to me.

How does it differ from regular D6?

Quote from: Joey2k;1113167How does it differ from regular D6?

You have to use the really tiny D6s.

Quote from: HappyDaze;1113169You have to use the really tiny D6s.

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Over the Edge - super simple, yet extremely flexible rules (easily compiled into a single page, including character generation), no need for anything but D6 and a setting that is just packing fun and adventure.

Advanced Fighting Fantasy
Fate  (Core & Accelerated)
Fudge
Mini-Six
WEG Star Wars
BRP OpenQuest
Capes, Cowls, & Villains Fowl
Sharp Swords & Sinister Spells
PDQ (egL Jaws Of the Six Serpents)
HeroQuest (2E)
RISUS

Out of those, for a light-crunch rpg, I would go with PDQ or HeroQuest if you like alot of scope to handwave and narrate, or go with Mini-Six if you like a bit of structure.
They are pretty rules-lite, and can cover most genres and tastes.

Quote from: Joey2k;1113167How does it differ from regular D6?

The Tiny d6 games by Gallant Knight Games all share the same basic system.  You roll 2d6 and if one of them comes up a 5 or 6 you succeed.  If you have an advantage for some reason, usually due to a trait, you get to roll 3d6.  If you have a disadvantage you only roll 1d6.

Characters generally are a stock archetype of some sort which give HP and maybe some pre-set traits.  You can then customize by picking a few more traits from the list.  So, for example, in Tiny Dungeon, there are no classes.  You pick a heritage (race) and then 3 traits.  You pick a weapon group you are trained in, a family profession and a belief.  Then you are off to play.

Numbers are kept really low.  Again, in Tiny Dungeon you will typically have between 4 and 9 HP.  Generally all damage is 1HP but that can be raised if you have the right trait. For example someone with Berserker can make an attack at disadvantage but does 2 HP damage if they succeed.  Tiny Supers tends to have a few other ways to raise damage via the superpowers.

What's really nice is that the books tend to have 1/3 to 1/2 the page count dedicated to micro-settings.  Basically 2-5 page setting guides that also give you a few rule tweaks or specific monsters.  So for roughly $20 you get a player's guide, a GMs guide, a monster manual and 15 or so setting outlines.

They have some smaller, more focused games, like Beach Patrol.  It's Baywatch the RPG, complete with random scenario generator and Baywatch Nights alternate setting.

Shadowrun Anarchy is great for one-shots and short adventures.

Cthulhu d20 is my go-to "basic version" of the d20 ruleset.